Once Prost retired, the rivalry disappeared between them I believe. Senna kept it all on the track, once Prost wasn't on it, he ceased to matter.
Great film, but at my age I was a Mansell fan, didn't appreciate Senna's talent, I just wanted a Brit to win!
Senna is rated usually above the Clarks, Fangios and Mosses of the F1 world simply because all his races were televised in glorious technicolour, you saw every overtake repeated with expert analysis. He was a true great though, with Prost, Mansell, Picquet and Berger on the grid he was still at the top. I think Schumacher would have outdriven him had he lived, it was about to happen with the rise of Benetton. But we'll never know for sure!